This invention relates to the diagnosis and treatment of undesirable tissue such as malignant tumors by certain drugs that accumulate in the undesirable tissue.
In one class of diagnosis and treatment with photosensitizing drugs, tumors are detected and treated by irradiating the tumors with light after the drug accumulates in the tumor. The drugs are photosensitizing and some of the drugs in this class are derivatives of hemoglobin.
There are several prior art techniques for such diagnosis and treatment. For example, in "Etudes Sur Les Aspects Offerts Par Des Tumeur Experimentales Examinee A La Lumiere De Woods", CR soc. Biol. 91: 1423-1424, 1924, Policard, the author, noted that some human and animal tumors fluoresced when irradiated with a Wood's lamp. The red fluorescence was attributed to porphyrins produced in the tumor. In "Untersuschungen Uber Die Rolle Der Porphine Bei Geschwulstkranken Menschen Und Tieren", Z. Krebsforsch 53:65-68, 1942, Auler and Banzer showed that hematoporphyrin, a derivative of hemoglobin, would fluoresce in tumors but not in normal tissues following systemic injection into rats.
In "Cancer Detection Therapy Affinity of Neoplastic Embryonic and Traumatized Regenerating Tissue For Porphyrins and Metalloporphyrins", Proc Soc Exptl Biol Med. 68: 640-641, 1948, Figge and co-workers demonstrated that injected hematoporphyrinwould localize and fluoresce in several types of tumors induced in mice. In "The Use of a Derivative of Hematoporphyrin in Tumor Detection", J Natl Cancer Inst. 26:1-8, 1961, Lipson and co-workers disclosed a crude material, prepared by acetic acid-sulfuric acid treatment of hematoporphyrin, said material having a superior ability to localize in tumors.
The photosensitive characteristic of tumor-selective porphyrin compounds also make them useful in the treatment of tumors. In "Photodynamic Therapy of Malignant Tumors", Lancet 2: 1175-1177, 1973, Diamond and co-workers achieved tumor necrosis after lesion-bearing rats were injected with hematoporphyrin and exposed to white light. In "Photoradiation Therapy for the Treatment of Malignant Tumors", Cancer Res. 38: 2628-2635, 1978, and "Photoradiation in the Treatment of Recurrent Breast Carcinoma", J Natl Cancer Inst. 62:231-237, 1979, Dougherty and co-workers reported using the crude Lipson hematoporphyrin derivative to accomplish photoradiation therapy on human patients.
The crude Lipson hematoporphyrin derivative has the ability to enter a variety of tissues and to be retained in tumor cells after it has mostly cleared the serum. Subsequent irradiation with red light excites the crude Lipson derivative which in turn excites oxygen molecules. The excited oxygen molecules exist for a microsecond--long enough to attack tumor cell walls and effect necrosis. In "Effects of Photo-Activated Porphyrins in Cell Surface Properties", Biochem Soc Trans 5: 139-140, 1977, Kessel explained that cross-linking of proteins in tumor cell membranes causes leakage and eventual cell disruption.
The crude Lipson hematoporphyrin derivative has several disadvantages such as: (1) it enters normal tissue and causes unacceptable damage to the normal tissue when therapeutic light sufficient to treat large tumors is applied; (2) it does not clear normal tissue sufficiently soon and thus some patients are harmed by exposure to ordinary sunlight as much as thirty days following treatment with the drug; and (3) it does not have an optimum absorbance spectrum in a range that penetrates tissue most effectively.